We have produced heterotopic urinary bladders in rats with an isograft inoculum of bladder fragments and air. Our research using this model has four specific aims: 1. To develop experimental procedures by which specific metaplastic changes, either squamous or glandular, will occur in the normal urothelium of the heterotopic bladder. 2. To compare implantation of transplantable bladder tumors on anatomically normal urothelium with implantation on squamous or glandular metaplastic urothelium. 3. To determine whether discrete foci of proliferative inflammation in the underlying stroma of heterotopic bladders induce corresponding foci of urothelial metaplasia and/or modify the local implantation of transplantable bladder cancer. 4. To produce multiple new discrete low grade tumors in individual heterotopic bladders so that we may subsequently modify the hosts, the pouches, or both, in order to identify and quantitate factors involved in tumor progression.